The main goal of Project #2 is to determine how precursor/stem cells develop in an in vivo transplantation environment. The tools for characterizing the cell populations before and after transplantation are laser capture microdissection (LSM). Expression arrays and morphology. The project also provides an opportunity to use gene expression arrays to better characterize human islet preparations in hopes of finding ways to better predict clinical outcome. Aim 1. Evaluation of human islet preparations for gene expression using LCM and gene arrays. Studies will be performed on in situ islets in the pancreas, on "healthy" isolated islets preparations and on less healthy islets. The work could lead to a practical simple test to determine the transplant potential of isolated human islets. Aim 2. Determination of the fate of human islets after transplantation. The major goal is to see in human precursor/stems contained in human islet preparations can form new beta cells in a graft site. The acute loss of beta-cells after transplantation will be determined and the remodeling of these grafts over time will be assessed. Aim 3. Differentiation of Transplanted Stem Cells (NIPs, ductal progenitors, SP cells, and others). It will be determine dif in vivo transplant sites provide a beneficial environment for the further development of precursor/stem cells that have been preconditioned in vitro.